I’ve maintained my very own email server and access for a few years. Admittedly it has been for secondary accounts and domains lately however for a few years from round 1993 it was my fundamental answer. I’ve by no means discovered a simple strategy to run these on macOS which is a disgrace. I additionally do not wish to go down Linux route because it turns into painful at virtually each step – it might be Unix-like however it’s no Apple!
My most popular possibility for small mail servers has at all times been VPOP3. I first got here throughout it round 1993 on CIX (convention system I’m on since 1988). The chap who develops it really works and runs the small enterprise and has plodded away for a few years incrementally bettering it. When mail grew to become a factor in 90s I put in this for a lot of shoppers and stored it at my very own enterprise for years (earlier than being persuaded to go to Exchange and that’s one other story ….).
A neat function it has at all times labored effectively with is assortment of mail from POP3 and help for multi-user POP3 accounts. Back in 90s this was nice – blink each hour and seize mail to maintain restricted POP3 account from filling and type at native stage. It additionally helps standard SMTP supply. The recordsdata and techniques used to retailer it are simply accessible and it has all kinds of choices. It consists of an IMAP/POP server so will work with any mail consumer (works fantastic with Apple for me) and has a webmail interface that may be very helpful. It is straightforward, straightforward to configure, tremendous dependable and does what it does. At £30 for five customers what’s to not like? It wouldn’t even start to pay for the time to contemplate the best way to setup on Linux.
Another possibility (sadly not macOS) is a Synology NAS with the superb mail providers. These can work much like VPOP and accumulate mail or take SMTP supply and provide native server, internet and so on. You can add different options by way of NAS reminiscent of time Machine server, file server, Plex server and so on.
One possibility I’ve typically considered on a Mac is to run VirtualBox most likely headless and run Windows 10 then VPOP and even Synology OS (which may be achieved although with doubtful legality very similar to macOS on non-Apple).
A last possibility could possibly be a Raspberry PI although I’m reluctant to recommend it. I just like the PI and it’s nice for what it does. Any time I begin to make it do issues past it is attain I discover it turns into pricey in $$/££ and time, unreliable and a bunch of problem. Given a small mini PC reminiscent of I run my Windows on (HP EliteDesk 800 i5 3.4Ghz 8GB 240GB SSD Windows 10 Pro picked up on eBay in pristine situation for £60+p&p) of infinity superior high quality is out there at what’s principally price of primary PI I might not recommend it.
Sorry this isn’t extra assist however hopefully one thing of curiosity. Happy to debate or help additional whether it is of any assist.